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Title:
SYSTEM AND METHOD FOR A TRAILER TOWABLE BY A VEHICLE
Document Type and Number:
WIPO Patent Application WO/2019/053021
Kind Code:
A1
Abstract:
The present invention provides a system for use in a trailer towable by a vehicle. The trailer comprises an axle having two wheels and at least one electric motor coupled thereto. The trailer and vehicle have complementary hitch components for coupling the trailer to the vehicle at a hitch of the trailer. The system comprises receiving means configured to receive a hitch coupling signal indicative of a state of the coupling between the hitch components. The system comprises processing means configured to determine whether the hitch components are uncoupled based on the hitch coupling signal. The system also comprises control means configured to cause the at least one electric motor to apply a force to the wheels to which it is coupled in response to a determination that the hitch components are uncoupled.

Inventors:
GREENWOOD, Jeremy (Patents Department W/1/073 Abbey Road Whitley, Coventry Warwickshire CV3 4LF, CV3 4LF, GB)
Application Number:
EP2018/074510
Publication Date:
March 21, 2019
Filing Date:
September 11, 2018
Export Citation:
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Assignee:
JAGUAR LAND ROVER LIMITED (Abbey Road Whitley, Coventry Warwickshire CV3 4LF, CV3 4LF, GB)
International Classes:
B62D59/04; B60L7/10; B60L15/32; B60T8/00; B60T13/00; B60W10/18; B60W10/26; B60W20/00; B60W20/13; B60W30/18
Domestic Patent References:
WO2008086087A22008-07-17
WO2003000538A12003-01-03
Foreign References:
US20020163249A12002-11-07
US20070260386A12007-11-08
US20130079980A12013-03-28
US20130079979A12013-03-28
Attorney, Agent or Firm:
LOCKEY, Robert (Jaguar Land Rover, Patents Department W/1/073 Abbey Road Whitley, Coventry Warwickshire CV3 4LF, CV3 4LF, GB)
Download PDF:
Claims:
CLAIMS

A system for use in a trailer towable by a vehicle, the trailer comprising an axle having two wheels and at least one electric motor coupled thereto, the trailer and vehicle having complementary hitch components for coupling the trailer to the vehicle at a hitch of the trailer, the system comprising: receiving means configured to receive a hitch coupling signal indicative of a state of the coupling between the hitch components; processing means configured to determine whether the hitch components are uncoupled based on the hitch coupling signal; and, control means configured to cause the at least one electric motor to apply a force to the wheels to which it is coupled in response to a determination that the hitch components are uncoupled.

A system according to Claim 1 , wherein the hitch components are determined to be uncoupled if the hitch coupling signal is not received.

A system according to Claim 1 or Claim 2, wherein the hitch coupling signal includes a signal from the vehicle.

A system according to any previous claim, wherein the signal from the vehicle includes a signal from a vehicle lighting subsystem.

A system according to any previous claim, wherein the hitch coupling signal is a wireless signal.

A system according to any previous claim, wherein the hitch coupling signal includes yaw sensor output data indicative of a level of trailer yaw from at least one on-board trailer yaw sensor, and wherein the processing means is configured to determine that the hitch components are uncoupled if the level of trailer yaw exceeds a predetermined threshold yaw value. A system according to any previous claim, wherein the hitch coupling signal includes positional sensor output data indicative of relative positions of the trailer and the vehicle from at least one on-board positional sensor of the trailer and/or vehicle.

A system according to Claim 7, wherein the at least one positional sensor includes at least one of a radar sensor and a vision sensor.

A system according to Claim 7, wherein the at least one positional sensor includes at least one accelerometer on the trailer and at least one accelerometer on the vehicle, and wherein the processing means is configured to determine that the hitch components are uncoupled if a comparison of positional sensor output data from the trailer and vehicle accelerometers indicates temporal divergence or convergence of relative trailer and vehicle positional data.

A system according to any previous claim, the receiving means being configured to receive coupling sensor output data from a coupling sensor configured to measure a coupling force exerted on the trailer by the vehicle, the coupling sensor output data being indicative of the state of the of the coupling between the hitch components, and the processing means being configured to determine whether the hitch components are uncoupled based on the coupling sensor output data.

A system according to Claim 10, the control means being configured to cause the at least one electric motor to apply a braking pulse to the wheels to which it is coupled, and the processing means being configured to determine that the hitch components are uncoupled if the applied braking pulse does not cause at least a predetermined level of change in the received coupling sensor output data.

A system according to Claim 1 1 , wherein the braking pulse is applied if the processing means determines that the hitch components are uncoupled based on the received hitch coupling signal. A system according to any previous claim, wherein the force applied to the wheels by the at least one electric motor is such that a speed of the trailer is reduced.

A system according to Claim 13, wherein the speed of the trailer is reduced to substantially zero speed.

A system according to Claim 14, wherein the trailer is controlled to reach substantially zero speed within a predetermined period of time and/or within a predetermined distance of travel of the trailer.

A system according to Claim 14, the receiving means being configured to receive trailer speed data indicative of the speed of the trailer, the processing means being configured to determine a maximum period of time and/or maximum distance of travel based on the trailer speed data, wherein the speed of the trailer is reduced to substantially zero speed within the determined maximum period of time and/or determined maximum distance of travel.

17. A system according to any of Claims 13 to 16, wherein each of the respective forces are braking forces.

A system according to any previous claim, wherein the force applied to the wheels by the at least one electric motor is such that the trailer follows a predetermined trajectory of travel.

A system according to Claim 18, wherein the predetermined trajectory of travel is a substantially linear trajectory.

A system according to any of Claims 1 to 17, the receiving means being configured to receive trailer trajectory data indicative of a current trajectory of the trailer, the processing means being configured to determine an uncoupled trailer trajectory based on the received trailer trajectory data, and the control means being configured to cause application of the force to the wheels by the at least one electric motor such that the trailer follows the uncoupled trailer trajectory.

21 . A system according to Claim 20, wherein the uncoupled trailer trajectory substantially corresponds to a current trajectory of the trailer.

22. A system according to Claim 20, wherein the received trailer trajectory data includes lane sensing output data indicative of lane markings in the vicinity of the vehicle, and wherein the determined uncoupled trailer trajectory substantially corresponds to a trajectory within the lane markings.

23. A system according to Claim 20, wherein the received trailer trajectory data includes road boundary output data indicative of a side of the road in the vicinity of the vehicle, and wherein the determined uncoupled trailer trajectory substantially corresponds to a trajectory in which the trailer moves towards the side of the road.

24. A system according to any of Claims 20 to 23, wherein the trailer trajectory data is received from at least one on-board sensor of the trailer and/or the vehicle.

25. A system according to Claim 24, wherein the at least one on-board sensor includes at least one of a laser sensor, an infrared sensor, and a vision sensor.

26. A system according to any previous claim, the system comprising the at least one electric motor.

27. A system according to Claim 26, the system comprising a first electric motor coupled to a first one of the wheels and a second electric motor coupled to a second one of the wheels.

28. A system according to any previous claim, the system comprising energy storage means configured to supply electric power to the at least one electric motor.

29. A system according to Claim 28 when dependent on Claim 26, the at least one electric motor being configured to act as a generator to charge the energy storage means when the force applied to the wheels is a braking force.

A method for use in a trailer towable by a vehicle, the trailer comprising an axle having two wheels and at least one electric motor coupled thereto, the trailer and vehicle having complementary hitch components for coupling the trailer to the vehicle at a hitch of the trailer, the method comprising: receiving a hitch coupling signal indicative of a state of the coupling between the hitch components; determining whether the hitch components are uncoupled based on the hitch coupling signal; and, causing the at least one electric motor to apply a force to the wheels to which it is coupled in response to a determination that the hitch components are uncoupled.

A trailer for being towed by a vehicle, the trailer comprising an axle having two wheels and at least one electric motor coupled thereto, and the trailer comprising a system according to any of Claims 1 to 28.

A trailer according to Claim 31 , comprising a first electric motor coupled to a first one of the wheels and a second electric motor coupled to a second one of the wheels.

A non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more processors causes the one or more processors to carry out the method of Claim 30.

Description:
SYSTEM AND METHOD FOR A TRAILER TOWABLE BY A VEHICLE

TECHNICAL FIELD The present disclosure relates to a system and method for a trailer towable by a vehicle. Aspects of the invention relate to a system, to a method, and to a trailer.

BACKGROUND It is common for a vehicle having motive power means, such as an internal combustion engine, that provides motive power to its wheels to also provide motive power to the wheels of a trailer. This may be in the context of a car towing a caravan or horse box, for example. Trailers may be provided with a mechanical over-run sensor that applies mechanically- coupled friction brakes of the trailer in response to braking, or a decrease in acceleration, of the vehicle. This assists the vehicle with reducing the speed of the trailer as appropriate. Such a mechanical over-run sensor operates only when the vehicle and trailer are moving in a forward direction. This means that a vehicle that is reversing, particularly downhill, or at rest on an uphill gradient, will receive no braking assistance from a trailer with a mechanical over-run sensor.

As the nature of the braking is mechanical as determined by the over-run trailer compared with the tow vehicle of the sensor, then the trailer will apply a destabilising force to the vehicle under braking. This can also result in swaying of the trailer behind the vehicle.

Also, a braked trailer may be connected to the tow vehicle by means of a break-away cable. This is designed to apply the trailer brakes in the event of the trailer becoming detached from the vehicle. However, the process of connecting the break-away cable can involve reaching under a bumper of the vehicle, which may be awkward for the user. It is an aim of the present invention to address one or more disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a system for use in a trailer towable by a vehicle. The trailer comprises an axle having two wheels and at least one electric motor coupled thereto. The trailer and vehicle have complementary hitch components for coupling the trailer to the vehicle at a hitch of the trailer. The system comprises receiving means configured to receive a hitch coupling signal indicative of a state of the coupling between the hitch components. The system comprises processing means configured to determine whether the hitch components are uncoupled based on the hitch coupling signal. The system comprises control means configured to cause the at least one electric motor to apply a force to the wheels to which it is coupled in response to a determination that the hitch components are uncoupled.

The present invention is advantageous in that one or more break-away conditions are identified by the system, which then uses the one or more electric motors to bring the trailer to rest as required by regulations while additionally ensuring that the trailer remains stable and follows a desired trajectory. This system eliminates the need for a break-away cable to be attached to the vehicle and trailer by the user. Advantageously, the force to be applied to the trailer wheels may differ in dependence on certain conditions, such as the particulars of the terrain over which the vehicle and trailer are travelling, weather conditions, etc. The system can receive inputs relating to the speed of the trailer wheels and so can correct the force applied to the trailer wheels to guard against trailer wheel slip while the trailer is being brought to rest.

The processing means may comprise an electronic processor and the receiving means may be an electrical input of the electronic processor, the electrical input being for receiving the hitch coupling signal. The system may comprise an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, the processor being configured to access the memory device and execute the instructions stored therein such that it is operable to determine whether the hitch components are uncoupled based on the hitch coupling signal.

The hitch components may be determined to be uncoupled if the hitch coupling signal is not received.

The hitch coupling signal may include a signal from the vehicle.

The signal from the vehicle may include a signal from a vehicle lighting subsystem.

The hitch coupling signal may be a wireless signal.

The hitch coupling signal may include yaw sensor output data indicative of a level of trailer yaw from at least one on-board trailer yaw sensor, and the processing means may be configured to determine that the hitch components are uncoupled if the level of trailer yaw exceeds a predetermined threshold yaw value.

The hitch coupling signal may include positional sensor output data indicative of relative positions of the trailer and the vehicle from at least one on-board positional sensor of the vehicle and/or trailer.

The at least one positional sensor may include at least one of a radar sensor and a vision sensor. The at least one positional sensor may include at least one accelerometer on the trailer and at least one accelerometer on the vehicle, and the processing means may be configured to determine that the hitch components are uncoupled if a comparison of positional sensor output data from the trailer and vehicle accelerometers indicates temporal divergence or convergence of relative trailer and vehicle positional data.

The receiving means may be configured to receive coupling sensor output data from a coupling sensor configured to measure a coupling force exerted on the trailer by the vehicle, the coupling sensor output data being indicative of the state of the of the coupling between the hitch components, and the processing means may be configured to determine whether the hitch components are uncoupled based on the coupling sensor output data. The control means may be configured to cause the at least one electric motor to apply a braking pulse to the wheels to which it is coupled, and the processing means may be configured to determine that the hitch components are uncoupled if the applied braking pulse does not cause at least a predetermined level of change in the received coupling sensor output data.

The braking pulse may be applied if the processing means determines that the hitch components are uncoupled based on the received hitch coupling signal.

Detection of the break-away condition(s) via the hitch coupling signal is advantageously cross-checked via the braking pulse so as to ensure a correct determination of an unrestrained trailer. The force applied to the wheels by the at least one electric motor may be such that a speed of the trailer is reduced.

The speed of the trailer may be reduced to substantially zero speed. The trailer may be controlled to reach substantially zero speed within a predetermined period of time and/or within a predetermined distance of travel of the trailer.

The receiving means may be configured to receive trailer speed data indicative of the speed of the trailer, the processing means may be configured to determine a maximum period of time and/or maximum distance of travel based on the trailer speed data, and the speed of the trailer may be reduced to substantially zero speed within the determined maximum period of time and/or determined maximum distance of travel.

Each of the respective forces may be braking forces.

The force applied to the wheels by the at least one electric motor may be such that the trailer follows a predetermined trajectory of travel.

The predetermined trajectory of travel may be a substantially linear trajectory.

The receiving means may be configured to receive trailer trajectory data indicative of a current trajectory of the trailer, the processing means may be configured to determine an uncoupled trailer trajectory based on the received trailer trajectory data, and the control means may be configured to cause application of the force to the wheels by the at least one electric motor such that the trailer follows the uncoupled trailer trajectory. The uncoupled trailer trajectory may substantially correspond to a current trajectory of the trailer.

The received trailer trajectory data may include lane sensing output data indicative of lane markings in the vicinity of the vehicle, and the determined uncoupled trailer trajectory may substantially correspond to a trajectory within the lane markings.

The received trailer trajectory data may include road boundary output data indicative of a side of the road in the vicinity of the vehicle, and the determined uncoupled trailer trajectory may substantially correspond to a trajectory in which the trailer moves towards the side of the road.

The trailer trajectory data may be received from at least one on-board sensor of the trailer and/or the vehicle. The at least one on-board sensor may include at least one of a laser sensor, an infrared sensor, and a vision sensor.

The system may comprise the at least one electric motor. The system may comprise energy storage means configured to supply electric power to the at least one electric motor.

The system may comprise a first electric motor coupled to a first one of the wheels and a second electric motor coupled to a second one of the wheels.

The at least one electric motor may be configured to act as a generator to charge the energy storage means when the force applied to the wheels is a braking force.

According to another aspect of the invention there is provided a method for use in a trailer towable by a vehicle. The trailer comprises an axle having two wheels and at least one electric motor coupled thereto. The trailer and vehicle have complementary hitch components for coupling the trailer to the vehicle at a hitch of the trailer. The method comprises receiving a hitch coupling signal indicative of a state of the coupling between the hitch components. The method comprises determining whether the hitch components are uncoupled based on the hitch coupling signal. The method comprises causing the at least one electric motor to apply a force to the wheels to which it is coupled in response to a determination that the hitch components are uncoupled.

According to another aspect of the invention there is provided a trailer for being towed by a vehicle. The trailer comprises an axle having two wheels and at least one electric motor coupled thereto, and the trailer comprises a system as described above.

The trailer may comprise a first electric motor coupled to a first one of the wheels and a second electric motor coupled to a second one of the wheels.

According to another aspect of the invention there is provided a non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more processors causes the one or more processors to carry out the method described above.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of a trailer towed by a vehicle, the trailer having a system according to an embodiment of an aspect of the invention, and showing the inputs to, and outputs from, the system; and, Figure 2 shows the steps carried out by the system of Figure 1 in a method according to an embodiment of an aspect of the invention.

DETAILED DESCRIPTION The present invention provides a system for a trailer towable by a vehicle via a hitch. The trailer and vehicle have complementary hitch components for coupling the trailer to the vehicle at the hitch. The trailer includes an axle having two wheels, where each wheel has an electric motor attached thereto. The system is arranged to receive a hitch coupling signal indicative of a state of the coupling between the hitch components, and arranged to determine whether the hitch components are uncoupled based on the hitch coupling signal. The system is arranged to cause each of the electric motors to apply a force to the wheel to which it is attached in response to a determination that the hitch components are uncoupled so as to bring the trailer to rest in a stable and controlled manner in the event that the trailer becomes detached from the tow vehicle.

Figure 1 shows a schematic plan view of a trailer 10 towed by a vehicle 12. The trailer 10 is connected to the vehicle 12 by means of a hitch coupling 14. The hitch coupling 14 is in the form of a mechanical hitch joint. In particular, a vehicle hitch component 16 is coupled or attached to a trailer hitch component 18 to allow the vehicle 12 to tow the trailer 10. For example, the vehicle hitch component 16 may be in the form of a tow bar and attached to the chassis of the vehicle 12. The tow bar can take the form of a ball, pin, hook or pintle. The trailer hitch component 18 may be a receiver-type component or a fixed drawbar-type component which can be hooked onto the tow bar so as to couple the hitch components 16, 18. The hitch components 16, 18 are such that relative pivoting movement between the trailer 10 and vehicle 12 is possible.

The hitch 14 comprises a hitch or coupling sensor 15 configured to measure a coupling force exerted on the trailer 10 by the vehicle 12. In particular, the coupling sensor 15 is arranged to measure both over-run and under-run of the trailer 10 on the tow vehicle 12. Over-run occurs when the trailer 10 applies a force in the forward direction to the vehicle 12, for example when the driver of the vehicle 12 applies the vehicle brakes when the trailer 10 and vehicle 12 are travelling in a forwards direction. Under-run occurs when the trailer 10 applies a force in the backward direction to the vehicle 12, for example when the driver of the vehicle 12 applies the vehicle brakes when the trailer 10 and vehicle 12 are reversing.

In the described embodiment, the vehicle 12 is a car having a plurality of on-board vehicle control subsystems and sensors. For example, the vehicle 12 includes a vehicle lighting subsystem 20 for controlling the external vehicle lights such as head lamps, brake lights and indicator lights. The lighting subsystem 20 receives inputs from the vehicle driver via control button and actuators within the vehicle cabin, and controls the external lights to operate as demanded. The vehicle lighting subsystem 20 is also connected to, and controls, trailer external lights 22 of the trailer 10. In particular, the vehicle lighting subsystem 20 is connected to the trailer external lights 22 by wiring connections 23. The vehicle lighting subsystem 20 is arranged to operate corresponding lights on the vehicle 12 and trailer 10 simultaneously. For example, if the driver depresses a brake pedal of the vehicle 12, the vehicle lighting subsystem 20 will control external brake lights on both the vehicle 12 and trailer 10 to operate.

The vehicle 12 includes an accelerometer 24. The accelerometer 24 may be part of a subsystem of the vehicle 12, for example a vehicle navigation subsystem, a vehicle speed control subsystem, or a vehicle electronic stability control subsystem. The accelerometer 24 can measure changes in the motion of the vehicle 12, for example measurement of cornering forces or noise, vibration and harshness (NVH) forces.

The vehicle also includes different types of sensors arranged to sense areas and objects in the vicinity of the vehicle 12. In particular, the vehicle 12 includes radar sensors in the form of laser sensors 26 and infrared sensors 28, and one or more vision sensors in the form of cameras 30. The radar and vision sensors 26, 28, 30 may be part of a subsystem of the vehicle 12. For example, the radar and vision sensors 26, 28, 30 may be part of a vehicle lane departure warning subsystem, in which the sensors 26, 28, 30 are arranged to detect lane markings on a road surface or a boundary of a road such as a pavement or a verge. Such a subsystem is arranged to warn the driver (via audio or visual warning signals, for example) or take corrective action if the vehicle 12 is determined to be leaving a particular lane without having indicated an intention to do so.

In the described embodiment, the trailer 10 has two wheels 40, 42, one on each side of the trailer 10, and connected by an axle 44. Each of the trailer wheels 40, 42 has an electric motor/generator or electric machine 46, 48 attached thereto. The electric machines 36, 38 are connected to the axle 44; however, they may be connected to the trailer 10 differently in different embodiments, for example via trailer wheel hub or frame connections. The electric machines 46, 48 are connected to, and powered by, a high-power, low-capacity battery 50 of the trailer 10. The electric machines 46, 48 may be used to apply regenerative braking or drive torque to the wheels 40, 42 of the trailer 10. In the described embodiment, the electric machines are configured to freewheel during normal driving of the trailer 10 and vehicle 12. The battery 50 is a lithium- titanate rechargeable battery: this type of battery is advantageous because of its fast charging time compared with other types of lithium-ion batteries.

Each of the trailer wheels 40, 42 also has a wheel speed sensor 52, 54 which measures the rotational speed of the respective wheel 40, 42. The trailer 10 also includes a yaw sensor 56 in the form of an accelerometer that is configured to detect the yaw, i.e. the angular velocity about a vertical axis, of the trailer 10. Like the vehicle accelerometer 24, the trailer accelerometer 56 can measure changes in the motion of the trailer 10, for example measurement of cornering forces or NVH forces.

Also like the vehicle 12, the trailer 10 includes one or more laser sensors 58, infrared sensors 60 and vision sensors 62 for sensing areas and objects in the vicinity of the trailer 10. The trailer 10 includes an electronic control unit or system (ECU) 70 configured to control the operation of the electric machines 46, 48. In particular, the ECU 70 comprises a receiver or receiving means 72, a processor or processing means 74, and a controller or control means 76. The receiver 72 is configured to receive electronic signals from components and subsystems of both the trailer 10 and vehicle 12. In particular, the receiver 52 receives signals indicative of a state of the coupling of the complementary hitch components 16, 18 at the hitch 14, that is, hitch coupling signals, as will be described further below. The processor 74 is configured to determine whether the hitch components 16, 18 are coupled or uncoupled based on the received hitch coupling signals. The controller 76 is configured to send control signals 78, 80 to the respective electric machines 46, 48 to cause each of the electric machines 46, 48 to apply a force to the trailer wheel 40, 42 to which it is attached in response to a determination by the processor 54 that the hitch components 16, 18 have become uncoupled. In this way, the electric machines 46, 48 can be used to apply regenerative braking to the trailer wheels 40, 42 to bring the trailer 10 to rest in a controlled manner if the trailer 10 becomes detached from the tow vehicle 12 during a journey.

Figure 2 shows a flow diagram outlining the steps of a method 100 undertaken by the processor 54. At step 102, the system 70 receives the hitch coupling signal from various sensors and subsystems of the trailer 10 and vehicle 12, the hitch coupling signal being indicative of a state of the coupling between the hitch coupling components 16, 18. For example, the hitch coupling signal includes a signal 82 from the external trailer lights connection. In particular, the system 50 monitors the state of the wiring connections 23 between the vehicle lighting subsystem 20 and the trailer external lights 22. In the event that the trailer external lights 22 become disconnected from the vehicle external lighting subsystem 20, the trailer external lights 22 are arranged to notify the system 70 via the signal 82. Alternatively, or in addition, the vehicle external lighting subsystem 20 is arranged to notify the system 70 of the disconnection via the signal 83, which can be a wireless signal.

The hitch coupling signal can also be sent to the system 50 in dependence on a wireless radio frequency signal sent between the vehicle 12 and trailer 10. In particular, the vehicle 12 has a wireless transmitter 84 and the trailer 10 has a wireless receiver 85. Specifically, the transmitter 84 is arranged to send wireless signals 86 to the receiver 85: if the transmitter 84 loses communication with the receiver 85 then a signal 87 is sent to the system 70 to notify the system 70 of the loss of communication, which is indicative of the trailer 12 having become uncoupled from the vehicle 10. It is not necessary that communication is lost between the transmitter 84 and receiver 85 for the hitch coupling signal 87 to be sent: for example, a detected increase in distance between the transmitter 84 and receiver 85 may result in the hitch coupling signal 87 being sent.

The hitch coupling signal can also be in the form of yaw sensor output signals 88, 89 from the vehicle yaw sensor 24 and the trailer yaw sensor 56. A detected temporal divergence or convergence in the respective levels of yaw in the trailer 10 and vehicle 12 may be indicative of the trailer 10 having become uncoupled from the vehicle 12 at the hitch 14. Alternatively, the hitch coupling signal 89 may be received from the trailer 10 only: the level of detected yaw in the trailer 10 increasing above a yaw threshold value may be indicative of trailer uncoupling, i.e. an unrestrained trailer. The hitch coupling signals 88, 89 from the trailer and vehicle accelerometers 24, 56 can include data relating to the respective positions of the trailer 10 and vehicle 12 other than yaw levels. For example, the signals 88, 89 can include positional data relating to cornering and/or NVH forces, with a temporal divergence or convergence of the difference between the respective positional data of the trailer 10 and vehicle being indicative of an unrestrained trailer. The hitch coupling signal can also be in the form of radar sensor output signals 90, 91 from the radar sensors 26, 28 of the vehicle 12 and/or the radar sensors 58, 60 of the trailer 10. The radar sensors 26, 28, 58, 60 can be used to detect the proximity of the trailer 10 to the vehicle 12: an increase in the distance between the trailer 10 and vehicle 12 above a distance threshold may be indicative of trailer uncoupling. Similarly, the hitch coupling signal can be in the form of vision sensor output signals 92, 93, with the vehicle and/or trailer cameras 30, 62 being used to provide data indicative of trailer uncoupling to the system 70.

Returning to Figure 2, at step 104 the processor 74 determines whether trailer 10 appears to have decoupled from the vehicle 12 based on the received hitch coupling signals 82, 83, 87, 88, 89, 90, 91 , 92, 93. Note that the processor 74 may make this determination based on one or more of these hitch coupling signals. When it is determined that the trailer 10 may be uncoupled based on the hitch coupling signal, the system 70 then attempts to verify this determination. Specifically, at step 106 the system controller 76 controls the electric machines 46, 48 to apply a pulse of regenerative braking to the wheels 40, 42 to which they are coupled. At step 108, the system 70 receives and monitors coupling sensor output data 94 from the coupling sensor 15. This is then used by the processor 74 at step 1 10 to confirm whether or not the trailer 10 has indeed decoupled from the vehicle 12. If the trailer 10 is still attached to the vehicle 12, then the applied braking pulse will result in the trailer 10 applying a drag force to the vehicle 12. In turn, this drag force will be sensed by the coupling sensor 15 and will be present in the coupling sensor output data 94. In contrast, the applied braking pulse will not register a force on the coupling sensor 15 if the trailer 10 is not attached to the vehicle 12. That is, if the drag force is absent from the coupling sensor output data 94 then the system 70 deems that the trailer 10 has indeed become uncoupled from the vehicle 12.

When it is confirmed at step 1 10 that the trailer 10 has become uncoupled from the vehicle 12, the trailer 10 needs to be brought to rest in a controlled manner. This may be done in a number of ways. For example, the unrestrained trailer 10 may be controlled based on its trajectory prior to the uncoupling. The preceding trajectory can be determined based on the coupling sensor output data 94 prior to the uncoupling. For instance, the sensed force at the coupling sensor 15 may indicate that the vehicle 12 and trailer 10 were following a curved path prior to uncoupling. Data from the radar and/or vision sensors 26, 28, 30, 58, 60, 62 of either or both of the trailer 10 and vehicle 12 may also be used to determine the trailer trajectory prior to uncoupling. The processor may then determine a future trajectory for the trailer 10 which involves controlling the trailer 10 to continue along the preceding trajectory while being brought to rest.

Another option is for the future trajectory of the trailer 10 to be a substantially straight line. That is, the trailer 10 is controlled to follow a straight or linear path while being brought to rest.

The system 70 may also utilise the lane sensing subsystems of the trailer 10 or vehicle 12 to determine a future trajectory for the trailer 10 upon decoupling. Specifically, the radar and/or vision sensors 26, 28, 30, 58, 60, 62 can be used to control the trailer 10 to remain in a lane based on road markings, or to move to the side of a road, while it is brought to rest. The system 70 may base the desired trajectory on the speed of the trailer 10. For example, the trailer wheel speed sensors 52, 54 provide wheel speed data in the form of signals 95, 96 to the system 70. In particular, the trailer 10 may be brought to rest over a longer period of time for a relatively high speed compared with a relatively low speed. The braking force applied by the electric motors 46, 48 may be greater for a relatively high speed than for a relatively low speed.

At step 1 14, the controller 76 causes the electric motors 46, 48 to apply respective forces to the trailer wheels 40, 42 in order to control the trailer 10 to be brought to rest in a controlled manner while following the desired or predetermined trajectory from step 1 12. In particular, the electric motors 46, 48 apply regenerative braking forces to the trailer wheels 40, 42; however, causing the trailer 10 to follow the desired trajectory may also involve the electric motors 46, 48 to apply a drive force to one or more of the wheels 40, 42 at various points. The trailer 10 may be brought to substantially zero speed within a period of time and/or within a distance of travel of the trailer 10. The period of time or distance of travel may be predetermined or may be based on the current trailer trajectory and/or speed. When based on the current trailer speed, the processor 74 may determine a maximum allowable distance the trailer 10 may travel before being brought to rest, or a maximum allowable period of time within which the trailer 10 should be brought to rest, and the electric motors 46, 48 brake the trailer wheels 40, 42 in accordance with the maximum distance or period of time.

Note that the present embodiment in which the electric motors 46, 48 are used to provide braking torque to the trailer wheels 40, 42 to bring the trailer 10 to rest in the event that it becomes uncoupled from the tow vehicle 12 can be used in conjunction with operating the electric motors 46, 48 to provide braking assistance and increased stability to the combination of the trailer 10 and vehicle 12, and/or to provide drive torque to the trailer wheels 40, 42 to provide pull away assist to the vehicle 12. Utilising the electric motors 46, 48 to provide drive torque will deplete the stored charge of the battery 50, while utilising the electric motors 46, 48 to provide regenerative braking to the trailer wheels 40, 42 will replenish the stored charge of the battery 50.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

In the described embodiment, the electric machines 46, 48 are powered by the battery 50; however, other energy storage means, such as one or many capacitors, supercapacitor or ultracapacitors, may be used in combination with or instead of the battery.

In the described embodiment, the vehicle lighting subsystem 20 is connected to the trailer lights by means of wire connections; however, in different embodiments the vehicle lighting subsystem may be wirelessly connected to the trailer lights. In particular, the vehicle lighting subsystem may receive inputs relating to the operation or status of the vehicle external lights. Also, the vehicle lighting subsystem may include a transmitter, for example a radio frequency transmitter, and the trailer may include a receiver, for example a radio frequency receiver, and the vehicle lighting subsystem transmitter is arranged to transmit the status of the vehicle external lights to the trailer receiver. The trailer external lights are controlled to operate in dependence on the received wireless signal. A loss of wireless communication between the vehicle transmitter and trailer receiver may be used as an indication that the trailer has become uncoupled from the vehicle in a similar manner to the transmitter 84 and receiver 85 in the described embodiment.

In the described embodiment, each of the two wheels (40, 42) of the axle (44) has a respective electric motor (46, 48) coupled thereto. That is, a first one of the electric motors (46) provides a drive or brake force to a first one of the trailer wheels (40), and a second one of the electric motors (48) provides a drive or brake force to a second one of the trailer wheels (42). However, in different embodiments a single electric motor may provide a drive or brake force to both of the wheels of the axle. For example, the trailer may be provided with gearing to allow the electric motor to provide power to both of the wheels of the axle. Note that although the trailer of the described embodiment has a single axle, in different embodiments the trailer may be provided with any number of axles and electric motors coupled thereto.